- EPYC 7501 All Core Boost Speed is specified to be 2.60GHz with TDP of 170W,

- EPYC 7551 All Core Boost Speed is specified to be 2.55GHz with TDP of 180W.

Is this slightly higher frequency along with a lower TDP in case of EPYC 7501 a result of a different internal architecture? Are those (clock frequency and TDP) the only differences between the 7501 and the 7551 model?

There is no architectural difference between the provided part numbers. Both of these part numbers are power limited at full threading, and while lower power workloads can run faster on the 7501, it is capped to 170W power tracking. The 7551, on the other hand, allows you to raise the TDP from 180W to 200W, by modifying cTDP in the BIOS, if the OEM designed the system cooling to allow for that TDP. By increasing the TDP on the 7551, it is possible to achieve higher overall performance depending on the workload.